Combined automatic unloader pilot and switch



Dec. 29, 1931.

'H. KERSHAW COMBINED AUTOMATIC UNLOADER PILOT AND SWITCH Filed April 23, 1929 2 Sheets$heet 1 AIR RECElVER OR TANK Dec. 29, 1931. Rs w 1,838,228

COMBINED AUTOMATIC UNLOADER PILOT AND SWITCH Filed April 1929 2 Sheets-Sheet 2 Zy.--Z. m

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t Harold Herskam;

Patented Dec. 29, 1931 HAROLD KERSI-IAVJ', OF QUINCY, ILLINOIS COMBINED AUTOMATIC UNLOADER PILOT .AND SWITCH Application filed April 23,

This invention relates to automatic controlling devices for compressors of air or other fluids, and especially to a combined automatic unloader pilot and switch.

One object of the invention is to provide an improved device which automatically stops or decreases the electro-motive power whenever a predetermined maximum pressure of the fluid is reached, and which automatically restores or increases the electro-motive power whenever the pressure of the fluid falls to a predetermined minimum, thereby maintaining an approximately uniform pressure at all times when the adjustment is unchanged.

Another object is to provide an improved combination of this character which is exceedingly quick and positive in its operations of controlling the electro-motive power, and also in diminishing the fluid pressure to a predetermined normal.

Other objects and important features are pointed out or implied in the following details of description, in connection with the accompanying drawings in which:

Figure 1 is a diagrammatic view showing the application of my invention in connection with a compressor provided with an unloader, an electric motor to operate the compressor, a fluid receiver or pressure tank, and the necessary electric connections and fluidpipes.

Figure 2 is a vertical sectional view substantially on the line 2-2 of Figure 4.

Figure 3 is a view similar to Figure 2, but showing the working parts in positions differin from Figure 2.

Figure 4 is a vertical sectional View along the line 44 of Figure 2.

Figure 5 is a horizontal sectional view through a somewhat modified form of the invention.

Referring to these drawings in detail, in which similar reference characters refer to similar parts in Figures 1 to 4, inclusive, the details of the invention will now be described as follows:

The main frame or casing includes three separable castings or parts A, B and C. The parts A and B are secured together by means of a headed and screw-threaded member D 1929. Serial No. 357,558.

which also constitutes a tubular bearing. The parts B and C are secured together by means of bolts or screws E.

A diaphragm F is clamped between the parts B and C, so these parts form separate 5 fluid pressure chambers 1 and 2. The part B is bored at 3 to form a seat for a valveseat member 4 which is peripherally recessed at 5, radially apertured at 6, and axially bored at 7. The valve-seat member 4 is tightly fitted in the bore 3, and clamped between the member A and the diaphragm F, so it cannot move from the effective position shown.

The member C is provided with an inlet opening 8 which is provided with screw threads for engagement with a pipe 9 through which the chamber 1 is in open communication with the air receiver or pressuretank, as shown in Figure 1. The member C is also provided with a bore 10 and with an outlet opening '11, the latter establishing an open communication between the bore 10 and the chamber 1. The outer end of the bore 10 is closed by a removable plug 12 which also constitutes a spring seat against which a compression spring 13 is seated for holding a valve-member 14 yieldingly seatedagainst the valve-member 4 so as to normally close the bore 7.

The member Bis provided with openings or passages 15, 16 and 17, the latter being provided with a needle valve 18 which is screw-threaded into the member B and provided with a lock-nut 19 for holding it in its different adjusted-positions. By means of this needle valve, the opening 17 can be choked or unchoked to the desired extent. The passage 17 is in open communication with the bore 5 and with the bore or passage 16, while the latter is in open communication with the pressure chamber 2, and has its outer end plugged, as shown at 20 in Figure 4. The opening or bore 15 is in screw-threaded engagement with a pipe 21 which con-" nects to the unloader (Figure 1) and is in open communication therewith, so compressed fluid passes from air receiver to the unloader only when the pressure in chamber lreaches its predetermined maximum and after deflecting the diaphragm F against the head of a plunger 22 which extends through the member D and is provided with an airtight packing 23. Air from the receiver passes through the pipe 9, chamber 1, valvemember 4 and pipe 21, to the unloader.

The plunger 22 bears againsta short arm of a lever 24 which is pivoted at .25 and trans mits motion to a link 26 to which it is piv o'ted at 27. The long arm of the lever 24 extends horizontally past the pivot 27 and connects to one end of a retractile spring 28 which has its other end connected to an ad justing bolt 28a. This bolt 28a extends through an opening 286 in the top of the easing member A, and has a nut .280 for coopera-tion therewith in tensioning the spring 28. I By means of this adjustment and ten-- sioning of the-spring 28, the maximum pressure of the fluid is determined, the m11umum pressure being determined by ad ustment of the needle valve 18.

;'l-he1link.26 has its intermediate part con- 'nected to one end of a retractile spring 26a which has its other end anchored at 26b, and at its upper end, it carries a roller 29 which rests against upper and lower cams 30 and 31 of a lever 32 on an axle or pivot 33. This lever 32 has a pivot 34 at its end opposite to the cams 30 and 31, and it also has a cam surface or (edge 35 substantially under the pivot '34. This cam edge 35 abuts against a plunger 36 which is slidable in a hollow boss 37 and constitutes a spring seat against which one .end'of 'a compression spring 38 is seated, while the other end of the compression spring bears against a valve member 39 which nor- ;mally closes the bore 7 of the valve member 4. A fixed lug or stop 40 limits the downward movement of the cam-edge 35 (as shown in Figure 3), while the upward movement of this cam edge is limited by the switch-mem-' .bers 45, 46, 47 and 48 (as shown in Figure 2). The hollow boss 37 is provided with a radial bore or outlet 41.

The operation of the device. as thus far described, will now be explained as follows When the predetermined maximum pressure causes the diaphragm F to press the plunger 22 inward, its power is transmitted to the lever 24, overcoming the elastic resistance of the springs 28 and 26a, and drawing the roller 29 down from the position shown in Figure 2 to that shown in Figure 3. Just before the roller 29 reaches its lowest position, it bears against the apex of the angle which forms the cam edges 30 and 31; and when its center passes slightly beyond said .a-pex, it cooperates with the cam edge 31 for instantly moving the lever 32 from the position shown in Figure 2 to that shown in Figure 3. This. operation of the lever 32 causes its cam edge 35 to depress the plunger 36, so the pressure of the spring 38 is increased and overcomes the pressure of the spring 13,

in consequence of the ends of the valve-members 14 and 39 abutting against one another; so these valveanembers move as a unit, and the bore 7 is closed by the valve-member 39 while the valve-member 14 moves away from the bore 7. This relation of the valve-memhers is clearly shown in Figure 3, and it will be seen that the fluid flows from the pressure chamber 1 through the openings 11, 10, 7, 6, 5 and 15 into pipe 21 and to the unloader. At the same time pressure is also admite l to secondary chamber 2 through openings 17 and 16, but is restricted by needle valve 18, in order to assist the power of the spring 28 to balance the gradually reducin pressure in chamber 1. The adjustment OI needle valve 18 determines this minimum pressure which permits the spring 28 to automatically return the lever 24 to the normal position shown in F ig-ure ,2. In returning to the normal or upper position, the lever 24 and link 26 cause the roller 29 to pass upward over the apex of the cam edges 30 and 31; and when it reaches the cam edge 30, the spring 26a causes the roller 29 and cam edge 30 to cooperate in moving the lever 32 to the position shown in Figure 2, wherein thecam edge 35 permits the pressure of the spring 13 to return the valve members 14 and 39 to the position shown in Figure 2. this position, the fluid pressure is released from the unloader and passes through pipe 21, and openings 5, 6 and 7 and out to atmosphere through outlet 41. ressure is simultaneously released from counter chamber ,2 by escaping to atmosphere through opening 16, past the valve 18, and thence through openings 17 and-41. From the foregoing explana tion of the operation, it will be seen that by adjusting needle valve 18 the pressure enter ing the secondary chamber 2 can be made to either maintain a constant pressure in the air receiver or vary the differential between wide limits very quickly and effectively as may be desired. I

Referring now to Figure 5, it will be seen that two sets of valves are provided, one valve of each set being connected by a bridge :or plate 42, so the valves are operated in unison by their springs 13 and 38. In this figure, all parts are the same as those described where similar reference characters are used; but it may be seen that the parts B1 and C1 have additional bores 3e and'10a,

respectively, 'and that the outlet opening or bore 41a is to release to atmosphere the pressure in the bleeder receiver, connected by pipe 43 to wall of the bore 10a. This bleeder receiver (not shown but well known) is some times used instead of a regular unloader and i is for the purpose of relieving the compressor of load for a brief period of time when start ing up by motor to allow full speed running before tull load is reached. When this form is used, :(Figure 5) pipe 21 is omitted and its threaded connection plugged. Bore 41 then independently thereof. Figure 1 shows the electric switch conventionally at S, while Figures 2 and 3 show it more in detail. An insulating member 45 is pivotally mounted on the cam-lever 32 and carries spring-pressed contacts 46. An insulating bar 47 is secured to the casing member A, and carries fixed contacts 48 which connect to the power line 49 and to the motor by means of wires 50, as shown in Figure 1.

From the foregoing description and explanation, it is evident that when the fluid pressure actuates the plunger 22 and the parts actuated thereby for reducing the fluid pressure, the same lever 32 that depresses the plunger 36 also lowers the switch members 45 and 46 and thereby opens the switch, so the motor stops actuating the pump or at least slows down, so the pressure very quickly reaches the predetermined minimum at which time the switch is again closed by the previously described operation of the lever 32.

Although I have described these embodiments of my invention specifically, it is not my intention to limit my patent protection to these exact details of construction and arrangement, for the invention is susceptible of various alternatives and modifications with out departure from the inventive ideas as implied and claimed.

lVhat I claim is:

1. In an unloader pilot, the combination of a casing including primary and secondary pressure chambers, a flexible diaphragm clamped between said chambers, a valvemember to establish and interrupt communication between said chambers, the primary chamber having an inlet for connection with the interior of a tank of compressed fluid, said secondary chamber having an outlet for expelling the compressed fluid therefrom, said secondary chamber having av fluid-tight bearing, a plunger in said bearing and operable by said diaphragm, and means operable by said plunger to actuate said valve-member, for the purpose specified.

2. In an unloader pilot, the combination of a casing including primary and secondary pressure chambers, a flexible diaphragm normally separating said chambers from communication with one another, a valve-member operable for establishing and interrupting communication between said primary and secondary chambers, means to communlcate Witha tank of compressed'fluid and to introduce such compressed fluid into said primary chamber, said secondary chamber having a valved outlet for expelling the pressure fluid, said secondary chamber having a wall provided with a bearing, a plunger seated slida-bly in said bearing and operable by said diaphragm, a lever having cam-edges on one end and forming an apex, a roller, means operable by said plunger to move said roller over said apex and thereby quickly move said lever from one extreme position co-the other extreme position, and means including a cam on said lever for operating said valve-member for the purpose specified.

3. The structure defined by claim 2, a compressor for introducing fluid into said tank and compressing it therein, an electric motor operatively connected to the compressor,

and an electric circuit including a switch, said electric circuit being connected to said motor and connectible to a source of electro motive power, said switch being operatively connected to said lever so as to be opened and closed thereby, for the purposes specified.

4. In an unloader pilot,'the combination of a casing including primary and secondary pressure chambers, a flexible diaphragm normally separating said chambers from communication with one another, said primary and secondary chambers being provided with a fluid-passage for establishing communication between them, a valve-member in said fluid-passage and normally closing the fluid-passage to'prevent such communication between the chambers, said primary chamber being provided with an inlet for connection with a pressure tank so as to introduce compressed fluid into the primary chamber, said secondary chamber being provided with a passage for communication with an unloader of a compressor, said passage having an outlet for the discharge of fluid from said secondary chamber and from said unloader, said secondary chamber having a bearing through a wall thereof, a plunger slidable in said bearing and operable by pressure against said diaphragm, and means operable by said plunger to move said valve-member for permitting pressure fluid to pass from said primary chamber to said secondary chamber.

5. In an unloader pilot, the combination of three casing members, a diaphragm clamped between two of said casing members and separating them to provide a primary pressure chamber and a secondary pressure chamber, said primary and secondary chambers being provided with a fluid-passage for communication between them, a valve-member in said fluid-passage, the thlrd'casmg member having a screw-threaded opening therethrough and having a tubular boss, a plunger slidable id tub a bese. e. be ng membe eatd n ee iel e -r w -tlnse ded epeei end ee ieg lat said ee nda 'y ehembe n e iee ive, to ecure the ee eedieey pre e eh m r te e l thied asi g member, a P ung i ble in s i e iie g an Opel-- able by said diaphragm under pressure of fl d. in s id- Pri r-y PBGSSIUB e mib r,

pr mary P e sur ehembe and a se d y pre ure ehamber, eme e mg mem e s egeth s su h 1 191 t a aid a the bore eeh ea ing m e i l ne w th t e here ei th Qt ee singm mb re, e val ee t-m mbe fixe n th b r v the nt m te en i the three ea m mhere, veheanemben. e pr ng 'her eeend one 0t thee-e e ing mem ers r u inea d valve-mem e to le e d val.ve-eeetme i i i er1 e Plung rth h re of t e thir on of the e e s lg m e n operable to meve a d valv mber fo open ng said v v -ee t-membe i nd mean op a l y aid. di ph agm fo op ra ng sai p mg r- In el er pil t th mbin i of hree s ng m mber ea h avi g ehe e, a

sWi eh-e ee ie meeheeiele he embineeiea w th. a valve and a w t h a h he n a movable member, of a lever pivotall suppen l -i at e pe i t b t en t ds en h a pivotal connection with the movable mber s id l w eh ha in Gem-edges 1v it lep eite ends, a pl e in nesition to be dep sedt e emeeee on o end o the eve and. te e tee eed me e e membex? eithe va ve, a ll e nk. err ing s id roller, a spring combining with said link for holding the roller against the cam-edge of the other end of the lever, and means to move the link in such manner that the said.

roller and adjacent cam-edge cooperate inv swinging said lever on its pivotal mounting and simultaneously actuating said movable members of; the switch and valve,

' In testimony whereof I affix my si nature.

HAROLD KERs; AW.

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